STM32F7: Add an OpenOCD board script for program/debug via SWD

scripts/openocd_gw_f7.cfg

@@ -0,0 +1,9 @@
+# OpenOCD board configuration for Greaseweazle STM32F730xx
+
+source [find interface/stlink.cfg]
+
+transport select hla_swd
+
+source [find target/stm32f7x.cfg]
+
+reset_config none